package Sort;

import org.w3c.dom.ls.LSOutput;

import java.util.Arrays;

//归并排序
public class MergeSort {

    //合并有序数组
    public static void merge(int[] a1,int i ,int iEnd, int j, int jEnd, int[] a2){
        int k = i;
        while (i <= iEnd && j <= jEnd ){
            if(a1[i] < a1[j]){
                a2[k] = a1[i];
                i++;
            }else{
                a2[k] = a1[j];
                j++;
            }
            k++;
        }
        if(i > iEnd){
            System.arraycopy(a1,j,a2,k,jEnd - j + 1);
        }
        if(j > jEnd){
            System.arraycopy(a1,i,a2,k,iEnd - i + 1);
        }
    }
    public static void sort(int[] a1){
        int[] a2 = new int[a1.length];
        split(a1,0,a1.length - 1,a2);
    }
    private static void split(int[] a1, int left, int right, int[] a2){
        //2.治
        if(left == right){
            return;
        }
        //1.分
        int m = (left + right) >>> 1;
        split(a1,left,m,a2);
        split(a1,m+1,right,a2);
        //3.合
        merge(a1,left,m,m+1,right,a2);
        System.arraycopy(a2,left,a1,left,right - left +1);
    }

    public static void main(String[] args) {
        int[] a = {9,3,7,2,8,5,1,4};
        System.out.println(Arrays.toString(a));
        sort(a);
        System.out.println(Arrays.toString(a));
    }
}
